The invention relates to a container. More particularly, the invention relates to the structure of a container for liquids.
Recent increases in bulk purchasing have created a demand for large-size containers. Many products, including liquids, are now sold to the consuming public in plastic containers that can be as large as 128 fluid ounces. Larger containers that hold heavy fluids, including beverages, home products, motor oil, or the like, must have a structure strong enough to withstand several different forces. Such forces include, for example, those that result from the weight of the fluid itself, rough handling during transportation, stacking during storage, and being dropped. Finally, large beverage containers that are filled by the hot-fill process must be structurally sound to withstand various forces relating to that process.
Some containers are cold-filled, while others are hot-filled. The hot-fill process is the procedure by which containers are filled with a beverage at a high temperature and capped soon thereafter. As the beverage cools within the container, stresses and strains develop in the container due to changes in the volume of the contents.
A container that is commonly used in the hot-fill process is the polyolefin continuous extrusion blow-molded container. Polyolefin continuous extrusion blow-molded container's are multi-layer containers that provide the requisite structure and barriers to oxygen and oils, for example. These multi-layered containers typically include an exterior layer of polypropylene or polyethylene as the main structure providing layer. Other layers can include oxygen barrier layers, moisture barrier layers, and regrind layers to provide the necessary barrier structures as well as adhesion between the layers.
It will be understood that to form a polyolefin continuous extrusion blow-molded plastic container, a parison can be heated in an extruder, captured by a mold, and blown in the mold. Specifically, to form the cavity of the container, a parison can be extruded up into the mold and as the mold comes together, a pneumatic blow pin, for example, can pierce the parison and blow the parison up against the walls of the mold. The mold typically contains flash pockets above and below the cavity in the mold to capture the excess of the parison that is forced above and below the cavity. When the parison is blown inside the mold, it is forced into the flash pockets and portions of the parison must adhere together. The excess flash can then be cut away from the container after it is ejected from the mold.
There is a need for a large container having a structure that can withstand, in particular, the top load forces that result from stacking of multiple layers of filled containers. In the case of hot-filled containers particularly, the structures should be capable of accommodating variations in volume of the containers' contents and changes of pressure and temperature. Furthermore, the structure should be capable of being manufactured in conventional high-speed equipment.